1. Field of the Invention
The present invention relates to medical devices and, more particularly, to methods and devices for forming a percutaneous channel. In one application, the present invention relates to a minimally invasive procedure to insert an orthopedic fixation or stabilization implant into the body, such as a formed in situ spinal stabilization rod.
2. Description of the Related Art
The vertebrae and associated connective elements are subject to a variety of diseases and conditions which cause pain and disability. Among these diseases and conditions are spondylosis, spondylolisthesis, vertebral instability, spinal stenosis and degenerated, herniated, or degenerated and herniated intervertebral discs. Additionally, the vertebrae and associated connective elements are subject to injuries, including fractures and torn ligaments and surgical manipulations, including laminectomies.
The pain and disability related to these diseases, conditions, injuries and manipulations often result from the displacement of all or part of a vertebra from the remainder of the vertebral column. A variety of methods have been developed to restore the displaced vertebrae or portions of displaced vertebrae to their normal position and to fix them within the vertebral column. For example, open reduction with screw fixation is one currently used method. The surgical procedure of attaching two or more parts of a bone with pins, screws, rods and plates requires an incision into the tissue surrounding the bone and the drilling of one or more holes through the bone parts to be joined. Due to the significant variation in bone size, configuration, and load requirements, a wide variety of bone fixation devices have been developed in the prior art. In general, the current standard of care relies upon a variety of metal wires, screws, rods, plates and clamps to stabilize the bone fragments during the healing or fusing process. These methods, however, are associated with a variety of disadvantages, such as morbidity, high costs, lengthy in-patient hospital stays and the pain associated with open procedures.
Therefore, devices and methods are needed for repositioning and fixing displaced vertebrae or portions of displaced vertebrae which cause less pain and potential complications. Preferably, the devices are implantable through a minimally invasive procedure.
In addition, a wide variety of diagnostic or therapeutic procedures involve the introduction of a device through a natural or artificially created access pathway. A general objective of access systems which have been developed for this purpose, is to minimize the cross-sectional area of the puncture, while maximizing the available space for the diagnostic or therapeutic instrument. These procedures include, among others, a wide variety of laproscopic diagnostic and therapeutic interventional procedures. Accordingly, a need remains for access technology which allows a device to be percutaneously passed through a small diameter tissue tract, while accommodating the introduction of relatively large diameter instruments.